as long as you have a tight handle, a good jumpshot and a good understanding of the game, then you can play pretty much until you physically are unable to run up and down a basketball court. Sure you may not be able to dunk and block many shots, but overall physical fitness is more than that. If you take care of your body earlier in your playing days you will be able to play a long time. I've played against guys in their 50s and they have all said the same thing: take care of your body.